A fluff control device such as that shown in FIG. 4 has been proposed in Japanese Patent Application No. 8-322222, which precedes the present application.
In the fluff control device according to the above application, yarn y is unwound from a stationary cop 1 produced by a spinning machine, upwardly in the axial direction of the cop 1, and is inserted, via a balloon control cylinder 2, into a guide hole 3a' of a support plate 3a of a control member 3, which comprises support plates 3a arranged in the vertical direction at a predetermined interval and having guide holes 3a', and a capsule tenser 3b sandwiched by the support plates 3a, and the yarn y then comes into contact with the circumferential surface of the capsule tenser 3b and is then supplied to a friction-disk-type false twister 4. Thereafter, the yarn y is wound via a yarn splicer 5 and a yarn clearer 6 around a cone-shaped winding package 8 rotated by means of a driving drum 7 while being traversed by means of a traverse device (not shown in the drawing).
The friction-disk-type false twister 4 provided on a yarn path between the cop 1 and the winding package 8 applies false twists to the yarn y, and in a twisting area that is located below the friction-disk-type false twister 4, the yarn y is twisted in a predetermined direction. The control member 3 arranged below the friction-disk-type false twister 4 controls the downward propagation of the twist below the control member 3, thereby effectively twisting the yarn y. Thus, by applying the false twists to the yarn y, the fluff protruding from the surface of the yarn y can be twisted in and be suppressed.
First of all, a description will be given with respect to the variations in tension in a conventional winding process in which the yarn y is unwound upwardly in the axial direction of the cop 1 and then wound around the cone-shaped winding package 8 rotated by the driving drum 7 while being traversed by means of a traverse device (not shown in the drawing).
As shown in FIG. 5, an empty cone-shaped bobbin 9 is supported by cradle arms 10, and a rubber ring 11 with a diameter larger than the long-axis diameter of the empty cone-shaped bobbin 9 is mounted to the bobbin holder 10a arranged at the cradle arm 10 on the long-axis diameter side of the empty cone-shaped bobbin 9. When the yarn y is first wound around the empty cone-shaped bobbin 9, the empty cone-shaped bobbin 9 does not contact the driving drum 7, but its rubber ring 11, which has a larger diameter than the long-axis diameter of the empty cone-shaped bobbin 9 does contact the driving drum 7. Thus, the empty cone-shaped bobbin 9 is rotated to allow the yarn y traversed by the traverse device (not shown in the drawing) to be wound around the empty cone-shaped bobbin 9.
As described above, the rubber ring 11 with a diameter larger than the long-axis diameter of the empty cone-shaped bobbin 9 contacts the driving drum 7 to rotate the empty cone-shaped bobbin 9 and the yarn y is wound around the empty cone-shaped bobbin 9. Once, however, the yarn layer formed around the empty cone-shaped bobbin 9 exceeds the outer circumferential surface of the rubber ring 11, the surface of the yarn layer wound around the empty cone-shaped bobbin 9 comes into contact with the driving drum 7 to rotate the winding package 8. Thus, the driving of the cone-shaped winding package 8 with the yarn layer formed therein is transferred from a drive based on the contact of the rubber ring 11 with the driving drum 7 to a drive based on the contact of the surface of the yarn layer of the winding package 8 with the driving drum 7. Thus, the yarn y unwound from the cop 1 is wound around the empty cone-shaped bobbin 9 to form the cone-shaped winding package 8.
The friction-disk-type false twister 4 will be described below mainly with reference to FIG. 4.
The friction-disk-type false twister 4 is structured so that a plurality of friction disks 4b are mounted onto three respective vertical shafts 4a disposed so as to appear to be positioned at the apex of a regular triangle when viewed from above. The friction disks 4b mounted onto the respective vertical shafts 4a are arranged so as to appear to be staggered when viewed from the side and so that part of each disk appears to overlap another disk when viewed from above (In FIG. 4, the vertical shaft located between and behind the two illustrated vertical axes 4a, as well as the friction disk mounted onto this vertical shaft, is omitted). The three vertical axes 4a are rotated in the same direction to twist the yarn y inserted between the friction disks 4b and bent in a zigzag manner.
As described above, the false twists are applied to the yarn y by means of a friction-disk-type false twister 4 provided on the yarn path between the supply bobbin 1 and the winding package 8. In the twisting area located below the friction-disk-type false twister 4, the yarn y is twisted in a predetermined direction. However, by means of the control member 3 arranged below the friction-disk-type false twister 4, the downward propagation of the twist below the control member 3 is controlled, thereby effectively twisting the yarn y. Thus, by applying the false twists to the yarn y, the fluff protruding from the surface of a yarn y can be twisted in and be suppressed.
The variations in tension occurring when the yarn from a single full package cop 1 is wound around the empty cone-shaped bobbin 9 will be described below mainly with reference to FIG. 6. The tension of the yarn y is measured by means of an appropriate tension measuring device T located near and between the yarn splicer 5 and the yarn clearer 6.
At the beginning of the winding of the yarn y around the empty cone-shaped bobbin 9, the friction disks 4b of the friction-disk-type false twister 4 are rotated to twist the yarn y that is stopped and set at a zero tension, while the empty cone-shaped bobbin 9 begins to rotate to wind the yarn y around the empty cone-shaped bobbin 9. Thus, the tension of the yarn y increases rapidly in a linear manner from a point (a) of zero tension to a point of tension (b), as shown in FIG. 6A. This process of increased tension continues until the yarn y reaches a constant running speed. During this interval, the friction disks 4b of the friction-disk-type false twister 4 gradually increase their rotation speed from a state of inactivity, and once they enter a steady state, the disks 4b continue to rotate at a substantially constant speed.
After the yarn y has reached this normal running speed, namely, after the point of the tension (b), the tension gradually increases to reach a point (c). This gradual increase in tension occurs because the yarn y is unwound from the cop 1 to reduce the diameter of the cop 1 while increasing the unwinding resistance of the yarn y from the cop 1.
Then, when the drive of the cone-shaped winding package 8 with the yarn layer formed therein is transferred from the drive based on the contact of the rubber ring 11 with the driving drum 7 to the drive based on the contact of the surface of the yarn layer of the winding package 8 with the driving drum 7 as described above, the tension of the yarn y increases rapidly in a linear manner from a point of tension (c) to a point of tension (d). This rise occurs because when the drive based on the contact of the rubber ring 11 with the driving drum 7 is transferred to the drive based on the contact of the surface of the yarn layer of the winding package 8 with the driving drum 7, the shorter diameter side of the winding package 8 rotating at a high circumferential speed first comes into contact with the driving drum 7, thereby rapidly increasing the running speed of the yarn y.
After the drive of the cone-shaped winding package 8 with the yarn layer formed therein has been transferred from the drive based on the contact of the rubber ring 11 with the driving drum 7 to the drive based on the contact of the surface of the yarn layer of the winding package 8 with the driving drum 7, the only variation in the tension of the yarn y is a minor increase in tension occurring because the yarn y is unwound from the cop 1 to reduce the diameter of the cop 1 while increasing the unwinding resistance of the yarn y from the cop 1 as described above. Thus, the tension gradually increases from the point of tension (d) to a point of tension (e).
When the amount of yarn y remaining in the cop 1 becomes very small, and in particular, when the final part of the yarn y wound around the bottom of the cop 1 is drawn out, the tension increases rapidly in a linear manner from the point of tension (e) to a point of tension (f). When all the yarn y in the cop 1 is used up, the tension obviously becomes zero, as shown by a point (g).
As described above, the tension significantly varies when the yarn y in the single full package cop 1 is wound around the empty cone-shaped bobbin 9 and the cone-shaped winding package 8 with the yarn layer formed therein, as shown in FIG. 6A. Then, the rotation speed of the friction disks 4b of the friction-disk-type false twister 4 increases in a linear manner from the inactive state to the steady state (A'), as shown in FIG. 6B, and after the rotation speed has reached the steady state (A'), it remains constant until the rotation is stopped after the exhaustion of the yarn y in the cop 1.
It is an object of the present invention to provide a tension control method using a fluff control device capable of reducing large variations in tension in the above conventional fluff control device to maintain a more constant tension.